This invention relates to food processing machinery, and, more particularly, to apparatus for extruding multiple streams of food products having fibers therein.
The extrusion of food products is an important technique for transforming a single mass of food product into multiple smaller pieces for further processing and eventual packaging for sale to consumers. In commercial production operations, some food products are most conveniently and economically prepared in a large mass, and the mass is then divided into smaller portions for subsequent processing. After initial preparation, the mass of food product is placed into a container having one or more extrusion ports, and the food mass is pressurized. Streams of the food product emerge through the ports and may be cut into shorter lengths.
Extrusion has been applied to the preparation of simulated jerky products such as strips of dried meat, particularly for use as pet foods. In preparing such a jerky product, a meat-containing mixture having a relatively high moisture content is mixed and then placed into an extrusion container, and a single stream of the meat mixture is extruded as a strip onto a supporting surface. The supporting surface with the strip of extruded meat mixture thereon is placed into a drying oven to dry the jerky by removing a major portion of the moisture, and the jerky is then cut into short lengths for packaging.
In the past, it has been known to extrude single strips of such a meat-containing product mixture onto a supporting surface, but it would be desirable to extrude multiple strips spaced closely together onto a supporting surface, to utilize the area of the supporting surface most effectively in the drying ovens. The extrusion of multiple strips of fibrous meat products having small spacings between adjacent strips has not been possible because of the fibrous content of the meat mixture. Even when processed, meat mixtures often contain meat fibers having lengths as great as about 1-2 inches. If multiple extrusion ports to the channels are placed closely together in the feed container, the long meat fibers can bridge over the wall between the adjacent extrusion channels at the ports, with the result that there is a buildup of fibrous material at the ports. This buildup rapidly leads to clogging of the extrusion channels at this station, and the apparatus must be shut down for cleaning. Extended and repeated downtime for cleaning essentially nullifies the advantages to be obtained from extrusion and particularly from the simultaneous extrusion of multiple product streams.
Additionally, it is necessary that the mass flow rate through each of the multiple channels be substantially the same. Otherwise, the final jerky product of different extrusion strips would have different densities and weights, an undesirable result for a mass-produced food product. If multiple ports are cut into a conventional feed container, wide variations are found in the weights of the final products discharged through various ports. There has been proposed no design for an extrusion apparatus which would allow extrusion of multiple, substantially identical, food product streams.
There thus exists a need for an apparatus to allow the simultaneous extrusion of multiple product streams of a food product containing lengths of fiber therein. While this need is most acute for the extrusion of meat products, preparation of other food products such as fibrous vegetable products also require such apparatus.
The difficulties in extruding multiple streams of a fibrous food mass have previously been recognized, as for example in U.S. Pat. No. 4,338,702. This patent describes an apparatus for forming a series of ground meat patties, with each patty formed by simultaneous extrusion of multiple plugs of a mass of meat product containing fibers. The apparatus described in the U.S. Pat. No. '702 patent forwardly extrudes a plurality of plugs from an extrusion chamber into a forming chamber, and then introduces a new mass of meat product into the extrusion chamber after the previously formed patty is moved out of the forming chamber. By the nature of the process, the meat extrusion function is periodically repeating rather than continuous. The specification of the U.S. Pat. No. '702 patent refers to the problem of the bridging of the meat fibers and buildup of fibrous meat mass. To solve the problem of the extrusion of multiple streams of the fibrous meat product, the U.S. Pat. No. '702 patent teaches (at col. 15) the loading of the next mass of food product in a reverse manner from the forming chamber through the extrusion channels and into the extrusion container. It is said that such reversing action wipes away the meat fibers bridging between the adjacent channels, thereby preventing fiber buildup. While this approach is said to be successful in accomplishing periodic extrusion, it obviously cannot be used for continuous extrusion operations, because the forward extrusion of the food mass into continuous multiple streams cannot be interrupted to load new product into the extrusion chamber in a reverse manner. Thus, while the problem of achieving multiple simultaneous extrusion of streams of food product from a fibrous food mass has been recognized and solved for one type of periodic extrusion, there has been proposed no approach which would allow continuous extrusion of such fiber-containing products.
Accordingly, there exists a need for an apparatus for performing the simultaneous, continuous extrusion of multiple, substantially identical streams of a food product from a single mass of the food product, where the food product has fibers therein whose greatest expected fiber length is greater than the minimum desired product spacing between the extruded streams of food prduct. The present invention fulfills this need, and further provides related advantages.